For a switching element employed in an inverter or the like, it is conventionally proposed a semiconductor device having an IGBT region, in which an IGBT element is arranged, and a diode region, in which a diode element is arranged (for example, see JP 2008492737 A).
Specifically, in the semiconductor device, a base layer is arranged at a surface layer portion of a semiconductor substrate providing an N− type drift layer. A trench gate structure is arranged to pass through the base layer. On a rear surface of the semiconductor substrate, a P type collector layer and an N type cathode layer are arranged. An N type emitter region is arranged at a portion of the base layer located above the collector layer.
On a front surface of the semiconductor substrate, an upper electrode, which is electrically connected to the base layer and the emitter region, is arranged. On the rear surface of the semiconductor substrate, a lower electrode, which is electrically connected to the collector layer and the cathode layer, is arranged.
That is, the IGBT region corresponds to a region in which the collector layer is arranged on the rear surface of the semiconductor substrate, and the diode region corresponds to a region in which the cathode layer is arranged on the rear surface of the semiconductor substrate. In other words, in the above semiconductor device, a boundary between the collector layer and the cathode layer corresponds to a boundary between the IGBT region and the diode region.
The IGBT region and the diode region are repeated alternately in one direction along a plane of the semiconductor substrate. The IGBT region and the diode region extend along a longitudinal direction perpendicular to the one direction in which the IGBT region and the diode region are repeated.
At a surface layer portion of the diode region of the semiconductor substrate, a damage region is arranged. The damage region is formed by irradiating He-ray to an entire surface of the semiconductor substrate.
In the above semiconductor device, a hole of the drift layer (i.e., an excess carrier) is recombined with an electron and eliminated in the damage region during the recovery time of the diode element. Therefore, the excess carrier, which causes a reverse current flowing to the diode element during the recovery time, is reduced, and the reverse current is decreased. Accordingly, a recovery characteristic of the diode element is improved.